Re: Benchmarking (was: Re: [MacPerl] crazy hoops to do something that seems so simple?)

[Ronald J Kimball <rjk@linguist.dartmouth.edu>]

On Wed, Nov 15, 2000 at 12:40:24AM -0500, Scott R. Godin wrote:
> on 11/14/2000 11:19 PM, Ronald J Kimball at rjk@linguist.dartmouth.edu
> wrote:
> 
> > Yup, you're right, you do need eval to use non-constant strings in tr///.
> > But fortunately, you only need the eval to be executed once.  For example:
> > 
> > my $reverse = reverse '0' .. '9', 'a'..'z';
> > my $trans = eval "sub { \$_[0] =~ tr/a-z0-9/$reverse/ }";
> 
> It wouldn't have occurred to me to put the reference where you did.. can you
> give me a clue or two as to why it's done that way instead of referencing
> the anonymous sub itself?

I'm not sure what you mean...  That does create a reference to an anonymous
sub.

Or do you mean the backslash before $_[0]?  That's inside double quotes;
the backslash escapes the dollar sign.  :)


> > Then, to avoid so many subroutine dereferences and calls, you can put the
> > loop inside the eval.  And if you're only going to execute the loop once,
> > you don't need the anonymous sub, of course; you can just eval the code
> > directly.  (See TransSub2 below for an example of that.)
> 
> hmm. I think, as I mention below, that it'd be $trans1 that I would use,
> however it occurs to me that you might have yet another trick to use, that
> would work in the context of my code. see my previous post to the list for
> the url. 

Not right now, but I might think of something later.  :)


> > And here's another benchmark, with various eval approaches:
> > 
> > 
> > Benchmark: timing 8192 iterations of Substitute, Trans, TransEval,
> > TransSub1, TransSub2...
> > Substitute: 26 wallclock secs (24.58 usr +  0.04 sys = 24.62 CPU)
> > Trans:       2 wallclock secs ( 1.30 usr +  0.01 sys =  1.31 CPU)
> > TransEval:   4 wallclock secs ( 3.96 usr +  0.01 sys =  3.97 CPU)
> > TransSub1:   2 wallclock secs ( 2.08 usr +  0.00 sys =  2.08 CPU)
> > TransSub2:   2 wallclock secs ( 1.22 usr +  0.00 sys =  1.22 CPU)
> 
> whew. 'nuff said. what computer are you running there anyway? (just curious)

~> uname -a
IRIX linguist 6.5 01221644 IP32

I haven't tried the benchmark on my Mac, I expect it would be somewhat
slower.


Ronald

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